Thermal conductivities of 3D braided carbon fiber/epoxy resin composites under different temperatures and braiding angles

Thermal conductivities of three-dimensional (3D) braided carbon fiber/epoxy resin composites are temperature-dependent and structure-sensitive. Here we report the influences of environment temperatures and braiding angles on the thermal conductivities. The thermal conductivities were tested on a self-designed setup and numerically simulated with a full-size geometrical model at microstructure level. We found that as the heat source temperature increases, the thermal conductivities of carbon fibers and epoxy resins increases, which in turn lead to the increases of axial thermal conductivity. At the same heat source temperature, with the increase of braiding angles, the temperature gradient becomes greater in the braided composites. The axial thermal conductivity is much greater than the transverse thermal conductivity. Furthermore, high temperature zones in the 3D braided composites localize in the central regions, i.e., the temperatures of interior carbon fiber regions are slightly higher than those of the surface and corner regions. Heat flux mainly transfer along the carbon fiber paths and then to the epoxy resin before the temperature equilibrium.